1. Field of the Invention
The invention relates to a power drill, more particularly to a power drill with a drill bit unit which is capable of providing intermittent axial impact during a drilling Operation thereof.
2. Description of the Related Art
A conventional power drill includes generally a drill bit unit, a driving unit for rotating the drill bit unit, and a speed reduction device which interconnects the driving unit and the drill bit unit so that the drill bit unit rotates at a speed smaller than that of the driving unit when the latter is actuated. In use, rotation of the drill bit unit of the conventional power drill may stop when an object which provides a retarding force that is greater than the torque of the drill bit unit is encountered. In this case, continued drilling operation of the drill on said object may ruin the conventional power drill because the torsion of the drill bit unit cannot be adjusted to overcome the retarding force. In some cases, it is necessary for the drill to pound the object in an axial direction of the drill bit unit during the drilling operation.